A memory cell includes a curved gate channel transistor, a buried bit line, a word line and a capacitor. The curved gate channel transistor has a first doped region located in a substrate, a second doped region and a third doped region located on the substrate, wherein the second doped region is directly on the first doped region and the third doped region is right next to the second doped region, thereby constituting a curved gate channel. The buried bit line is located below the first doped region. The word line covers the second doped region. The capacitor is located above the curved gate channel transistor and in electrical contact with the third doped region. The present invention also provides a memory cell having a vertical gate channel transistor, and the vertical gate channel has current flowing downward.